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物质的鉴别是中学化学学习的重点之一,其方法有多种,要分清鉴别的类型,掌握解题的规律,才能解答好试题。一、一剂鉴别(限用一种试剂来鉴别多种物质)1.原理:选用一种试剂分别加入到待测物质中,会出现明显不同的现象。2.方法:(1)若物质有明显的溶解性差异、溶解时的热效应差异以及水溶液颜色的差异时可用“水”来鉴别,如:鉴别CaCO3、aOH、NaCl;(2)若物质有明显的酸碱性差异,可选用指示剂或pH试纸来鉴别,如:鉴别HCl、Ca(OH)2、NaCl;(3)鉴别一组溶液时:若
The identification of substances is one of the focuses of chemistry study in middle school. There are many ways to distinguish them, so it is necessary to distinguish the types of identification and master the rules of problem solving in order to answer the questions. First, a reagent identification (limited to a reagent to identify a variety of substances) 1. Principle: The use of a reagent were added to the test substance, there will be significantly different phenomenon. 2. Methods: (1) Identification of CaCO3, aOH, NaCl if substances have significant differences in solubility, differences in thermal effects on dissolution, and differences in color of aqueous solutions can be identified by “water” There are obvious differences of acidity and alkalinity, which can be identified by using indicator or pH test paper, such as: identification of HCl, Ca (OH) 2, NaCl; (3)